This invention relates to a mixed solvent that is especially suitable for use together with a wiping cloth to remove sealing compositions (alternatively called "sealers"), especially poly{vinyl chloride}, rubber, epoxy resin, and/or acrylic based sealers that are used in "body shop" and "paint shop" areas of automobile manufacturing plants, from the surfaces of automobile bodies at various stages of the manufacture of the auto bodies.
Sealing compositions are initially readily deformable solids, which alternatively could be called highly viscous liquids, that can easily be inserted into joints and the like. Sealing compositions are used during the manufacture of auto bodies before any general chemical treatment of the overall metal of which auto bodies are primarily constructed and often also at later stages, e.g., after one or more stages of painting. The method of use of the sealers is sufficiently imprecise that almost inevitably some of the sealer will be accidentally applied to some part of the automobile where it is not desired, along with the places where it should go. Also, the sealing compositions eventually are converted to no longer readily deformable solids during the course of manufacture of a complete automobile by the action of heat and/or lapse of time. In the course of this manufacture, residues from these sealing compositions, with varying degrees of deformability, can exude from the locations where they are desired to remain in the final product onto the parts of the auto body surfaces that need a decorative finish in the final automobile.
In order to prevent surface blemishes that might result from areas of sealer on the part of the surface of an automobile that is to be given a decorative finish, it is customary to wipe the auto body at several stages during the process of its complete manufacture with cloth or some similar soft, conformable, and retentively porous material that contains as absorbate a suitable solvent or solvent mixture to assist in transferring any portions of sealing composition(s) that could interfere with later decoration of the surface to the solvent containing wiping cloth, which is eventually discarded. The same or a similar type of wiping cloth is also used to remove dust from sanding at various stages of manufacture. Various solvents have been used for such wiping cloths in the past, but none has been entirely satisfactory.
One problem with the prior art solvents used for this purpose is that the same type of wiping cloth with the same solvent content is normally used throughout all stages of manufacture, including a wipe after the application of cationically electrodeposited paint, a step that is usually only one or two steps from the end of the process of completing the most decorative finish on an auto body exterior, and sometimes even a wipe of the very last decorative finish applied ("top coat"). Some solvents very readily dissolve the uncured sealer compositions, which usually include, for example, poly{vinyl chloride} and/or acrylic polymers, filler(s), and sometimes plasticizer(s). Such solvents would be very desirable to have in a wiping cloth used while most of the auto body surface is still bare metal, but such solvents are likely to attack the electrodeposited paint layer and any subsequent paint layer and therefore can not be used at that stage. Other problems with prior art solvents and solvent mixtures used in wiping cloths include: unpleasant odors; an evaporation rate that is too slow, so that solvent remains on the surface wiped more than about 30 seconds after wiping is finished, or too fast, so that most of the solvent is gone from the wiping cloth before the operator has finished the wiping operation; and fire hazard from the use of solvents with low flash points.
Accordingly, one major object of this invention is to provide a solvent mixture particularly useful in wiping cloths for the removal of poly{vinyl chloride} and/or acrylic based sealing compositions that will avoid or minimize at least one, and most preferably all, of the difficulties noted above that exist with prior art products. Other objects, which include provision of a wiping cloth incorporating this superior solvent mixture and processes for the use of the solvent and/or the wiping cloth, will be apparent from and be further explained in the description below.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word "about" in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred, however. Also, throughout the description, unless expressly stated to the contrary: percent, "parts of", and ratio values are by weight or mass; the term "polymer" includes "oligomer", "copolymer", "terpolymer" and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or of generation in situ within the composition by chemical reaction(s) noted in the specification between one or more newly added constituents and one or more constituents already present in the composition when the other constituents are added, and does not preclude unspecified chemical interactions among the constituents of a mixture once mixed; specification of constituents in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole and for any substance added to the composition; any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to an object of the invention; the word "mole" means "gram mole", and the word itself and all of its grammatical variations may be used for any chemical species defined by all of the types and numbers of atoms present in it, irrespective of whether the species is ionic, neutral, unstable, hypothetical, or in fact a stable neutral substance with well defined molecules; and the terms "solution", "soluble", "homogeneous", and the like are to be understood as including not only true equilibrium solutions or homogeneity but also dispersions that show no visually detectable tendency toward phase separation over a period of observation of at least 100, or preferably at least 1000, hours during which the material is mechanically undisturbed and the temperature of the material is maintained within the range of 18-25.degree. C.